From 4c659ff7e85ef03cc292a1b7113e482921f61fea Mon Sep 17 00:00:00 2001
From: Neven Sajko <s@purelymail.com>
Date: Wed, 4 Mar 2026 14:25:38 +0100
Subject: [PATCH 1/4] simplify `firstrest` using `Iterators.peel`

`Iterators.peel` is supported on all Julia versions supported by
IterTools. In fact, it was already present with Julia v0.7.
---
 src/IterTools.jl | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/src/IterTools.jl b/src/IterTools.jl
index 8499fa6..3aeeaf9 100644
--- a/src/IterTools.jl
+++ b/src/IterTools.jl
@@ -128,11 +128,9 @@ julia> collect(r)
 ```
 """
 function firstrest(xs)
-    t = iterate(xs)
+    t = Iterators.peel(xs)
     t === nothing && throw(ArgumentError("collection must be non-empty"))
-    f, s = t
-    r = Iterators.rest(xs, s)
-    return f, r
+    return t
 end
 
 # Iterate through the first n elements, throwing an exception if

From 158dcc6f33d43c4508b27f21fb39d17acd6ec7dd Mon Sep 17 00:00:00 2001
From: Neven Sajko <s@purelymail.com>
Date: Sun, 8 Mar 2026 11:31:56 +0100
Subject: [PATCH 2/4] deprecate `firstrest`

---
 src/IterTools.jl | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/IterTools.jl b/src/IterTools.jl
index 3aeeaf9..5dab9ad 100644
--- a/src/IterTools.jl
+++ b/src/IterTools.jl
@@ -128,6 +128,7 @@ julia> collect(r)
 ```
 """
 function firstrest(xs)
+    Base.depwarn("`firstrest` is deprecated in favor of `Iterators.peel`", :firstrest)
     t = Iterators.peel(xs)
     t === nothing && throw(ArgumentError("collection must be non-empty"))
     return t

From d96f4a18c1b90608e948ab81659d91a2892f2646 Mon Sep 17 00:00:00 2001
From: Neven Sajko <s@purelymail.com>
Date: Fri, 27 Mar 2026 13:52:11 +0100
Subject: [PATCH 3/4] just make it an alias

---
 src/IterTools.jl | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/src/IterTools.jl b/src/IterTools.jl
index 5dab9ad..c7d92a0 100644
--- a/src/IterTools.jl
+++ b/src/IterTools.jl
@@ -113,7 +113,7 @@ end
 
 Return the first element and an iterator of the rest as a tuple.
 
-See also: `Base.Iterators.peel`.
+Alias for `Base.Iterators.peel`.
 
 ```jldoctest
 julia> f, r = firstrest(1:3);
@@ -127,12 +127,7 @@ julia> collect(r)
  3
 ```
 """
-function firstrest(xs)
-    Base.depwarn("`firstrest` is deprecated in favor of `Iterators.peel`", :firstrest)
-    t = Iterators.peel(xs)
-    t === nothing && throw(ArgumentError("collection must be non-empty"))
-    return t
-end
+const firstrest = Iterators.peel
 
 # Iterate through the first n elements, throwing an exception if
 # fewer than n items ar encountered.

From 1c61fb9852431f2576eafa0b4cc93fc01bd20d0d Mon Sep 17 00:00:00 2001
From: Neven Sajko <s@purelymail.com>
Date: Fri, 27 Mar 2026 13:58:38 +0100
Subject: [PATCH 4/4] update test

---
 test/runtests.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/runtests.jl b/test/runtests.jl
index 2b375dc..b802f1d 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -36,7 +36,7 @@ include("testing_macros.jl")
         ]
 
         @testset "$xs" for (xs, s) in test_empty_cases
-            @test_throws ArgumentError firstrest(xs)
+            @test nothing === firstrest(xs)
         end
     end